1. Field of the Invention
This invention is in the field of progressive dies for forming sheets of metal.
2. Description of the Prior Art
Heat transfer fins include collared holes which receive coolant tubes. The collars surrounding each hole are secured to the coolant tubes providing a unified construction as well as effective heat transfer. Traditionally, the collared holes are produced by extending a punch through the fin and drawing or stretching the material outwardly from the main body of the fin. The drawing operation may result in undesirable metallurgical properties. I have therefore devised a method and die for producing a collared hole minimizing the drawing of the metal. The method and die disclosed herein forms the collar by means of bending metal outwardly.
The height of each collar surrounding a fin hole depends on final product requirements. As a result, the punch and bushing used to form the collar must be changed for each different collar height. Disclosed herein is a progressive fin die designed to produce collared holes of varying heights through the selection of a main punch extendible through a pattern of holes initially formed in the sheet of material.